You’ve probably heard whispers about the benefits of using citric acid as a hair rinse. But does it really work? The truth is, healthy hair naturally leans towards a slightly acidic pH. Nami Ikkuma, a renowned beauty editor specializing in hair care, explains that one of the reasons why bleach, hair color, and perms can damage hair is because they disrupt this natural pH balance.
Hair cuticles, the protective outer layer of each strand, are closed when the pH is acidic. However, when the pH becomes alkaline, the cuticles open up, allowing coloring and perming agents to penetrate. This is why repeated coloring and perming can leave your hair with a persistent alkaline tilt, making it difficult to return to its natural state.
Ikkuma highlights that environmental factors like UV rays and dry air, along with the habit of overwashing, can exacerbate this issue. Hair that struggles to return to its natural, slightly acidic state becomes drier and more prone to damage. This is where citric acid steps in. Its unique ability to neutralize the alkaline buildup and restore a more acidic environment in your hair helps tighten cuticles, leading to smoother, more manageable tresses.
But how does citric acid achieve this? The key lies in the structure of keratin, the primary protein in hair. Keratin is composed of amino acid chains known as polypeptides, which are intricately linked together to form a complex 3D structure. These links are categorized by their strength, with hydrogen bonds being the weakest and peptide bonds being the strongest. Ikkuma explains that water weakens hydrogen bonds, making hair feel softer when wet, and these bonds re-form when hair dries, resulting in a firmer texture.
Ionic (salt) bonds are particularly susceptible to breakage when the pH shifts during coloring and bleaching, contributing to dry, damaged hair. Stronger disulfide bonds, disrupted by perming treatments, lead to limp, lifeless hair. The most resilient peptide bonds, once broken, are difficult to repair, leading to split ends and breakage.
Citric acid primarily targets the weaker hydrogen and ionic bonds. Hair is structured in three layers – the outer cuticle, the cortex, and the medulla. Damaged hair often experiences ‘hollowing’ in these various layers. Due to its small molecular size, citric acid can penetrate deep into the cortex, reaching the damaged areas. Moreover, citric acid boasts three ‘carboxyl groups’ (COOH groups), which act like three hands, reaching out to repair broken bonds within the hair, effectively boosting internal repair and strengthening the structure.
Beyond its hair repair capabilities, citric acid’s safety profile is another reason to embrace it. It’s already widely used as a pH regulator, and its safety is well-established as it can be consumed in food, used in supplements, and applied topically. Knowing that a substance is safe for both consumption and skin contact makes its application in hair care even more appealing. Our scalp, with its numerous pores and large sebaceous glands, is particularly adept at absorbing what we apply to it. Considering past instances where ingredients initially believed to be beneficial for hair were later found to have negative health consequences, ‘safety’ is a crucial factor to prioritize.
Nami Ikkuma, a beauty editor and hair-diagnosis instructor, is a prominent voice in the hair care world. She actively contributes to magazines, newspapers, and online platforms, conducts seminars, and collaborates on hair care product development. Her published works include “Good White Hair Care, Terrible White Hair Care” (Shogakukan) and “The Beginning of Dye-Free White Hair” (Graphic Sha). @namiikuma_hairista
